Re: Spyder MR100 Feedneck
Take your feedneck off the marker and take it down to Home Depot, Lowes, or any other local hardware store that sells loose screws (or screws in baggies). Compare the screw to the hole and find one that'll fit, then a nut to match the threads that'll fit. I believe the stock size is metric, but there is almost always a standard equivalent.
If you call Kingman, the part number is SCR048. They simply refer to it as a "Feed Neck Clamp Screw & Nut" in the manual.